The present invention relates to the collection of light from a high numerical aperture (N.A.) source and reforming the light into a lower N.A. point source for coupling into an optical system.
Most modern illumination sources, such as bulbs, light emitting diodes and arc lamps are extended sources that radiate light in a spherical or hemispherical pattern. Standard refractive optics can transmit or focus a portion of the source light but at a substantial loss, typically greater than 70%. Standard reflective optics possess better efficiencies but essentially still lose 50% of the total light. With the ever increasing cost of energy, it will be important to generate and utilize light as efficiently as possible. To that end, light will preferably be shaped, controlled and otherwise manipulated, and then placed within the desired area and function with as little loss as possible. Such conditions call for the use of light coupling technologies. Exemplary applications for light couplers include fiber optic delivery systems, defined area illumination, non-laser based collimated Sources, and life science technologies illumination.
The ability to refract or reflect light from a high N.A. format to a low N.A. format can be done in a straight forward manner; a simple lens held in front of a bulb accomplishes this. The light emanates from the lens either diverging, converging or collimated. However, only a small percentage of the total light generated is captured for use, typically 12.5% for an F/#−1.0 lens. The goal is to convert the high N.A. light source into low N.A. light source while reforming the light into a point source or quasi point source (i.e. an extended source whose emission area is small with respect to the optical system stop). Implementing such a system is complex and can require a bulky apparatus. Typically, the solution is to restrict the amount of light captured, or greatly increase the aberration of the reconstituted point source. In general, currently available light coupler techniques are a compromise between the amount of effective light gathering ability and the complexity of the optical mechanisms.